Radiocarbon dating marine sediments

10-Jun-2017 20:10

Ages of core top sediments range from 2000 to 21,000 14C yr B. Some 'old' core top dates are from piston cores and probably represent the loss of sediment during the coring process, but some core top samples 6000 14C yr B. Statistical analysis on an a posteriori design indicates that geographic area is the major cause of variability; there is a difference in mean surface sediment age of nearly 2000 yr between sites in the western Ross Sea and sites east of Ross Bank in south-central Ross Sea.

The systematic variability in surface age between areas may be attributed to: (a) variable sediment accumulation rates (SAR) (surface age is inversely related to SAR), (b) differences in the percentage of reworked (dead) carbon between each area, and/or (c) differences in the CO2 exchange between the ocean and the atmosphere.

The majority of these are either in correct stratigraphic order or, where this is not the case, within the 2 range of adjacent dates.

Regardless, groups of between five and six consecutive (with respect to depth) radiocarbon ages define consistent linear sedimentation rates with a high degree of confidence ( 0.9) for the late Holocene and part of the LGIT period.

High-resolution radiocarbon dates, magnetic susceptibility and lithostratigraphic evidence from a lake sediment core from Nedre Hervavatnet located at Sygnefjell in western Norway provide a record of the early Holocene.Chironomids, leaves produce the most consistent results.Sedimentological and physical properties of the core suggest that three meltwater events with high sedimentation rates are superimposed on a long-term trend with glacier retreat between 97 cal BP.Two different trends can be seen in the tree ring series.First, there is a long-term oscillation with a period of about 9,000 years, which causes radiocarbon dates to be older than true dates for the last 2,000 years and too young before that.

High-resolution radiocarbon dates, magnetic susceptibility and lithostratigraphic evidence from a lake sediment core from Nedre Hervavatnet located at Sygnefjell in western Norway provide a record of the early Holocene.

Chironomids, leaves produce the most consistent results.

Sedimentological and physical properties of the core suggest that three meltwater events with high sedimentation rates are superimposed on a long-term trend with glacier retreat between 97 cal BP.

Two different trends can be seen in the tree ring series.

First, there is a long-term oscillation with a period of about 9,000 years, which causes radiocarbon dates to be older than true dates for the last 2,000 years and too young before that.

However, in 1958, Hessel de Vries was able to demonstrate that the ratio had changed over time by testing wood samples of known ages and showing there was a significant deviation from the expected ratio.